Rolled copper alloy article



April 21, 1942. c, E. SWARTZ ETAL 2,280,103

' RoLLED COPPER ALLOY ARTICLE Filed Dec. 9, 1939 4 sheetsshet 1 I/vvE/vro/s. D CARL VSVARTZ y BY oNALn CHW/Erz 'AUGE/vm@ April 21, 1942. c. E. swARTz ET AL ROLLED COPPER ALLOY ARTICLE illed Dec. 9, 1959 INvENTo/Qs. CARL E. SwAm-z 5y' DONALD L.\/.$cHwv/\Rrz ATTORNEYS.

April 21, 1942. c; E. swARTz Erm. v 2,280,103

ROLLED COPPER ALLOY ARTICLE Filed bec. 9, 1959 4 sheets-sheet s JNVENTORS. A CA RL E. SWARTZ BY DONA/ D L V SCHWARTZ A TTOfiNEYS APllZl, 1942 y c.E.`swAR1-z E-rAL 2,280,103

ROLLD COPPER ALLOY ARTICLE Filed Dec. 9, 1939 Y 4 Sheets-Sheet 4 A5 CAST -IOOX J/VVENTORS. CARL E. SWARTZ 5y o/VALD L VScHwA/rz ATTORNEYS.

" "aourncorrsasrmrsanelin Cari-E. swam. cleveland nemmeno nonna n.

V.- Sohwartz, Cleveland, Ohimasllgno ev'eland VGraphite Brome' Company, (lleversto'lhe I land, pino, a corporation ofOliio lThe 'present invention'relating to rollable alioys i'sparticularly'directed' tothe manufacture l:of copper alloys oftwo or more' constituents such l' as copper and leadtfor copper, lead and tin,\capa ble'of being'rolled in'what may be termed coinmercial rolling practice. Our process maybe applied also to the manufacture of either-copper alloys bythem'selves-or to 4these alloys `reinforced 7 by a' layer of steel.' The essence'of the invention, we believe to be, the discovery that when copper alloysfsu'ch as leaded bronze or copperlead,are castwithcertain structural characteristics,` thealloys` may be rolled `by' commercial rolling practices such as certain' ones used and generally known in brass mills. v.

-According to our information none of the brass mills furnishes `iolledleaded materials containing more than 'about 4% lead. o The reason for this is vthat even 4% lead'in the alloy increases rolling dimculties. It is known Ythat certain castings roll with comparativeease-'while others are almost; if not impossible, to work. The exact reason for this isnot known beyond the fact that the difference lies in structural peculiarities; Attempts to roll copper alloys containing large f Application December o, recast-,rm No. 303,444

" (clumsy, ,e I

. section, aft`er".af5`0%4 reduction withoutl crack.- i

Fig. 4' is a similar view of still another alloy;

" 1 Fig. 5` isa photomicrograph showing they structure of'an alloy to be described in the as cast" "condition:

Fig, 6 is a similarview, Vbut showing. the struc- "ture of an alloy after annealing; and

Fig. 7 is a similar view showing the structure of the material after annealing but ywith a 50% reduction.

In general, ,the structure of the alloy in the .fas cast condition which renders the same capable of being commercially rolled is as follows: In alloys consisting of two or 4more phases chanical and chemical. By way of illustration,

we will take'a leaded bronze containing the constituents: lead 840%; tin 4-10%;'zi nc20"%2 copper, remainder. In the as cast" condition,'.v

` there are three or more phases usually present:

amounts of lead have thus far been unsuccess- 1 ful `except by. the methods herein described.

To the accomplishment of the foregoing and related-rendspsaidinvention. then. consists of showing Vthe appearance oi an alloy which will" be described, (la) in the as cast''vlcondition in cross section, (1b) the structure after a 50% reduction in thickness by rolling'(1c) the as' ycastcondition at the surface and 1d) .the struc- -ture atter a 50% reduction on anenlarged scale,

respectively;

Figs. 2a, 2b, 2c and 2d are photomicrographs showing the condition of a second alloy, (2a) inthe as cast condition in cross section, (2b) a structure after a 50% reduction, (2c) the as o cast, condition at the surface and (2d) the structure aitera 50% reduction on an enlarged scale, respectively. Fig. 3 isa photomicrograph oi another alloyl showing the appearance of the alloy in cross (1) the high lead or softphase; l(2) the alpha or-copper-richl phase; (3) a pseudo-phase rich in copper but higher in tin (and zinc if present) than the alpha phase and solidifying'at a lower. .temperature than the alpha. The last material (3) is `also considerably harderthan. material (2). Alloys of `this general composition havey been-known to metaliurgists for many years; but

. only in thecast condition. Repeated prior attempts to roll this alloy hate been unsuccessful. In lorder to coldroll such alloys commercially,

we have found that certain structural conditions are desirable. f 4

1. The lead should be surrounded `hy av phase sui'iicientiy resistant to deformation so that when subjected telthe pressure incident to vrolling, this phase will coniine the lead and not allow it to form into stringers, that is, thin bands of lead r the pseudo-phase is quite thick, rolling has actually been accomplished wherein the lead particles were elongated less than the alpha phase. Where only two phases are present. namely a lead-rich and a copper phase, rolling is more 2 A difficult but 1f conditions 2) and 4) named telow are present, rolling may be effected.

2. Durlng'solidication, we have found it desirable that crystallization takes place in such a way that the dendritic crystal growth is s ubstantially continuous through the thickness and `.normal tothe direction of rolling.

To avoid a substantial amount of porosity in .ajcast article it is desirable to produce a cooling of the molten metal from one surface toward an opposite surface. Such cooling produces dendrites extending substantially parallel to each other from one surface. To secure these results lt is necessary, as will be-evident from the present descriztior, to cause a controlled .solidication of lthe metal at-one surface and proceedingv toward an opposite surface, and by the term controlled as herein used is meant a solidiflcation which is not necessarily uniform as regards time, but which is uniform as regards the progress of the solidifying front of metal from one surface toward the opposite surface. For

example, there might be uniform cooling inthe in the term controlled cooling or controlled o solidication as herein used.

3. 'Ihe hard pseudo-phase should tend to form an interdendritic net workl through the structure.

4. The lead phase shouldbe dispersed throug the structure in particles not too large. a

` harder phase.

for this alloy usually calls for 'Z to 9% lead, 3.5 to 4.5% tin, .01 to 4% zinc, and the balance substantially copper. In Fig. la the material is shown in the as cas condition, in cross section, at one hundred magniflcations. This material is cast against a steel backing strip or support 5 and solidicatlon is produced bythe method described in our coperiding application, Se-

rial No. 308,228, filed December 8, 1939. The result of this method of solidiflcation will be obvious from the microphotograph which shows a number of substantiallyV parallel dendrites extending in a direction normal to thev surface of the steel supporting member 5. In this figure, there appear particles of lead 3 dispersed throughout the material and surrounded by a The remainder of the material lying between the lead particles surrounded by their protective coating of the pseudo-phase is an alpha copper phase. Fig. 1b shows the same material after a reductionby rolling of 50% and at the same magnification. In this gure, the lead particles 3,-:at .theleft of the figure, can be distinctly shown and have been drawn out, buthave not been allowed to form stringers or to flow together by reason of the harder protective pseudo-phase. It is only the occasionally n extra large lead particles which can be clearly It 4will be apparent to thoseskilled in the art particles. Since this material is that which is most easily drawn out'under a rolling pressure that such factors are obtained by controlling 'the forming stringers, these particles should be enclosed in a harder material or phase and it is desirable that this phase (2) "in turn be harder than the remainder (l) of the composition. The structure of the as cast material or phase is such' that there is an orientation of the dendrites, as shown in Fig. la, producing directional properties and the-phase I is weak, which makes it easier for the phase 2 to prevent the excessive deformation of the lead. If these conditions, exist, rolling of the' material will produce a structure in which the particles 3 of the softest constituent may haveI been elongated, but as they are enclosed by the material or phase 2, which is the hardest of the three constituents,

distinguished in this microphotograph, but it will be noticed .that the particles of lead are in the main, small and distributed through the metal.

In Fig.lc, there is shown the surface of the alloy referred to in the as cast" condition and here again it will be noted that the lead particles are in the main, small andwell distributed through themetal.

Fig 1d is a microphotograph showing the same material after a reduction but under magi niflcation of 350, which will,'of course, magnify the differences in size of the lead particles. Even atV such magnification, however, the bulk of ,the lead particles are small and well distributed throughout the material 'and have been protected against the formation of stringers by the harder coating of the pseudo-phase.

In Figs.'2a, 2li, 2c and' l2d are shown microphotographs Iof a second alloy,- the photograph corresponding to those of Figs. 1a, lb, 1c and ld. This second alloy consists of approximately 80% copper,- 10% tin and 10% lead. The specification for this alloy usually. calls for 9 to 11% lead, 9 to 11% tin, .01 to 5% zinc, and the balance substantially copper. Fig. 2a shows the structure of the material in the ,as cast" condition which corresponds closely to the structure of the material shown in Fig. 1a. Similarly, Fig. 2b shows the material altera 50% reduction and corresponds closely to material shown in Fig. la. Fi'g, 2c

l shows t he structure of the material as cast at they have not produced stringers which might cause cracking of the material. If there is a proper` dispersion of the softest particles and ifthese are properly enclosed within they hard` phase, the entire material may be rolled without detrimentalcracki-ng since the s'oft particles are not allowed to form points of weakness or long drawn stringers in the material.

If we refer now to Figs, 1a, 1b, 1c and ld, there arer shown` photomicrographs of an alloy conthe surface with good distribution of the lead. and Fig: 2d shows the material after a 50% reduction undermagniflcation'of 350, and again we' nd the lead phase well distributed.

In'Fig. 3 there is shown still another alloy of the same general character and containingl a larger amount of lead and of approximately the' following analysis:

Ber-cent Copper.` 72 vLead' 20 Tin 8 This view shows the metal after a 50% reduction without cracking, ata magnification of and there is to be noted a satisfactory distribution of the original cast structure.

` acconcialeadV particles and 'the `absence of serious stringers; 'fr w Fig; 4 is a' similar nview `showing still another approximateanalysislas follows:

alloy containingstill more lead and having the A ,J 4 i Ber-,dent Copx: er i l 1 6'1 to 74" Lead Y y i i 22l/2 to 27 1/2 'Iin 3 to 4 -A maximum of 3%,zinc h In this view the metal -is shownafter a 50% reduction without cracking. Although some of the lead particles are definitely elongated, it is remarkable with so much lead: present to find that the protective action of the hard phase has effectively prevented the formation of detrimental stringers.` 1

While the above are illustrations of commer- I cialiy rollable structuresin particular alloy compositions, our invention is by no means limited to such alloys. For example,incertain systems or under certain cooling conditions; the phases analogous to the two copper phases discussed above, may not form, but a single phase which is cored may replace them. Coring takes place by` a change of composition during cooling such that the highest melting and softest material f crystallizes ilrst and is in turn surrounded by a lowerl melting and harder material but Anot crystallizing as a new and discrete phase. However, itis important that the soft phase be sur- `rouridedrfby a material ofra relative greater hardness `or rresistance to deformation sufilcient to prevent excessive elongation of the lead. Itis also important that the dendrites be relatively uniform in size and extend substantially through the thickness of the work normal to rolling diintotwo oit-more sections, fthenjt will. be found that the lead will segregate at these points which are points of weakness.. During rolling, the-structure will open up at these npoints and the @lead will` form 4into Astringers whichv cannot be'removedy satisfactorily in later'operations. If the dendrites are not substantiallyparallel, the structure willalso be found to be weak and will not deformk uniformly during rolling,` -resulting incracks.` f

` To-illustrate the.foregoing,we mayrefer to Figs. 5, 6, and 'l of. which Fig. 5 kshows the same composition as that already described -in Figs. 2a, 2b,\2c andf2d. `The metal of Fig.'5 is shown .inthe as cast" condition. lIn Fig. 6 the ,same

metal is shown `afterannealing, and we may here note the disappearance of the dendritic structure. After annealing, the material ...as

shown in this figure presents the same favorable ance substantially copper;

containing lead in an amount. up to as much as rection. While it is, of course, desirable that pockets, caused by entrapped gas or, precipitated gas be absent and that interdendritic shrink be absent, these defects are .not as detrimental to oursuccessful Vrolling as under the present cornmercial casting and rolling conditions.

As would be expected by those skilled in' the art, once suchrmaterial is rolled'down and andistribution of the lead but the pseudo-phase has disappeared, being replaced by equiaxed grains due to the recrystallization of themetal.

This material is now in condition for rolling, and in Fig. '7, the 'same'material is shown after a reduction. yWe here find the leadv phase elongated in the direction of the rolling and the slip lines throughout the alpha copper phase, but no cracking appeared and no formation of detrimental lead stringers. f

It has been found that leadcontaining valloys having the characteristics herein described and containing lead in amounts from 3% to 7%` can be made `and rolled with uniformfsatisfactory results. An alloy of this type, which we have successfully rolled, falls within the rangeof 3 to 7% lead, 31/2 to 5% tin, .01 to 5% zinc, and the bal- Copper-lead alloys 4% of lead are, in some cases, now made and rolled but many mills refuse orders for such material and the mills which will accept such orders may experience heavy losses in rolling, and

produce, in some cases, from 30% to 40% ofy scrap material due to the formation of stringers nealed at the usual annealing temperatures for y copper alloys, or for steel, if it be steel backed, the recrystallized structure is quite different from Dendrites are absent and the matrix is now composed Yof unstrained grains. The lead particles are more or.

lessrounded and lie at the grain boundaries of the copperkphase. Coring has disappeared as has the pseudo-phase. This new structure is workable by ordinary commercial practice such as that used for rolling low lead-copper alloys.

` I This workability, we attribute to the substantial absence of flaws or discontinuities in the copper phase, and the favorable dispersion of the completely separated lead particles. During deformation the lead deforma to the same extent as the copper phase but only to the same extent,

i. e. there are no cavities or cracks in the copper y,

phase into which the lead can beV internally extruded to form detrimental stringers.

When the casting has the preferred structure heretofore described, it may also be possible to roll the material after anv annealing which destroys the pseudo-phase. Rolling cannot be accomplished, however, unless the cooling has approached the'conditions described previously;

that is forming individual dendrites continuous through the thickness normal to rolling. Should thedendrites not be continuous but segmented and cracks in the rolled material. The lpresent invention contemplated the casting of a material in which; as already described, the soft particles, that is `in the last case, the lead, is so enclosed in hard/er deformation resistant shells that it will not string out or produce cracks during rolling.

to about 25% of lead substantially uniformly distributed throughout a matrix 'and elongated in a direction parallel to the direction of rolling, the article being substantially free from detrimental lead stringers.

2. A rolled copper alloy article resulting from axproductwhich has been unidirectionally cooled during solidiflcation and reduced at least 5% of its'original thickness containing from about 3% to about '1% of lead substantially uniformly distributed throughout amatrix and elongated in a direction parallel to the direction of rolling,

4 the. article being substantially free from detrimental lead stringersi` 3. A composite strip comprising a strip of steel having bonded thereto a layer of a copper alloy resulting from a product which has been unidirectlonally cooled during solidiiication and reduced atleast 5% of its original thickness and containing from about 5% to about 25% of lead substantially uniformly distributed throughout a matrix and elongated in a direction parallel to the direction of rolling, said layer of copper alloy being substantially free from detrimental lead stringers. y y

4. A rolled copper alloy article, resulting from a product which has been unidirectionally cooled of copper, the lead being substantially uniformly distributed throughout a matrix and elongated in a direction parallel to the -direction of rolling, the article being substantially free from detrimental lead stringers.

6. A rolled alloy article resulting from a product which has been unidirectionally cooled during solidiilcation, said article consisting of 31/2 to 5% of tin, .01 to 5% of zinc, 3 to 7% of lead,

' with the balance substantiallylcopper, the lead,

being substantially uniformly distributed throughout a matrix and elongated in a direction parallel-to the direction of rolling the article beingf'substantially free from detrimental lead stringers.

7. A rolled alloy article resulting from a prod-- uct which has been unidirectionally cooled during solidification, said article consisting of 'l to 9% lead, 31/2 to 41/2% tin, .01 to 4% zinc, with the balance substantially copper, the'lead being substantially uniformly distributed throughout a matrix and elongated in a direction parallel to the direction of rolling, the article being substantially free from detrimental lead stringers.

8. A rolled alloy resulting from a product which has been unidirectionally cooled during solidification, said article consistingv of 9 to 11% lead, 9 to 11% tin, .01 to .5% zinc, and the balance substantially copper, the lead being substantially uniformly distributed throughout a matrix and elongated in a direction parallel to the direction of rolling, the article being substantially free from detrimental lead stringers.

CARL E. SWARTZ. DONALD L.A V. SCHWARTZ. 

